When Robin and Ted are the only two members of the group to show up to a night of baking pies, they notice that they have nothing to talk about when they are together, creating a nagging feeling that they are no longer really friends, but end up having sex out of awkwardness.
When Ted and Robin arrive at Marshall and Lily's apartment for Thanksgiving, they reveal separately to their friends what happened.
Later during dinner Bob uses the phrase "major buzzkill", and Ted and Robin absent-mindedly salute, causing them to realize there is still a connection between them and they can still be friends.
Future Ted tells his kids that since he had a great evening with his friends (and Bob), he takes them to Marshall and Lily's to spend Thanksgiving every year.
Barney begins to taunt dismayed Marshall as the slap countdown enters the last ten seconds.